1. Field of the Invention
This invention pertains to magnetic recording diskettes, specifically to a liner or cleaning fabric contained within the shell or jacket of the diskette.
2. Background of the Invention
Magnetic recording diskettes are commonly used for word processing and personal computer applications where relatively inexpensive, random access data storage is desired. These diskettes generally have a flexible disk of magnetic recording material substantially enclosed in a plastic shell. The shell is designed to protect the magnetic recording surface from exposure to contaminants such as dust, smoke, hair and fingerprints which can disrupt the operation of the head. However these contaminants do enter the shell through the access window or the hub opening. To minimize the effect of the contaminants a diskette liner can be placed inside the shell to wipe the disk surface as it rotates.
The liner is typically a soft nonwoven fabric cut to fit the inside of the shell and to allow head access to the recording medium. An effective liner must have the ability to clean the disk surface (remove and hold stray particles and contaminants) while not causing scratching or excessive wear to the disk over millions of revolutions in the drive. Equally important, the liner should not itself be a source of debris that could contribute to the possibility of signal error or loss of data.
Liners are frequently made from nonwoven fibers bonded together with an adhesive binder. Such liners typically contain between 20 and 50% by weight of binder. Unfortunately the binder while improving fabric integrity also stiffens the fabric and can cause scratching of the magnetic layer.
Thermal bonded nonwoven fabrics have been used, but such fabrics either suffer from much higher debris levels or require additional processing steps or multilayer structures. U.S. Pat. No. 4,998,176 (Takemae) and U.S. Pat. No. 5,060,105 (Howey) suggest improving thermal-bonded, nonwoven liners by treating the fabrics with less than 10% and less than 5% binder, respectively. Such treatment is reported to yield diskette liners with decreased debris in comparison to nonwoven liners that were thermally bonded only. The Takemae patent indicates a preference for greater than 1% binder and shows examples only at the 5% binder level. The Takemae patent also teaches that the binder is found primarily in the part of the fabric which is not thermocompression bonded.
The Howey patent teaches a non-woven fabric which is spot welded at the thermal bond points. Howey indicates a preference for binder levels between 1.5 and 3.0% by weight of the fabric and teaches that the binder is found preferentially at the junction points of the fibers. Both the Howey and the Takemae patents show substantial increases in flexural rigidity after the addition of the binder material to the nonwoven fabric.